Prevention of foaming in steam generation



Patented Jan. 3, 195% UNITED STATES PREVENTION OF FOAMING IN STEAMGENERATION No Drawing. Application October 28, 1944,

Serial No. 560,899

2 Claims.

This invention relates to a method for conditioning water and, moreparticularly, for eliminating foaming conditions in steam boilers.

Foaming of boiler water is not, as commonly thought, equivalent to anaccumulation of foam on top of the surface of the boiler water. Whensteam is rapidly withdrawn from a boiler with resultant foaming, thereis no Water surface within the boiler correlated with the water levelindicated in the conventional water glass attached to the boiler. Inother words, there is no sharp line of demarcation between solid waterand foam in a boiler during rapid steam withdrawal.

The foaming of boiler water is actually a rapid expansion of the waterin a steam generating area of the boiler brought about by the fact thatrapidly forming small steam bubbles do not coalesce until a definiteshort time after their formation. As a consequence, the entire volume ofwater in the generating area is expanded by myriads of bubbles until thethus formed socalled light water may fill the steam space and becomeentrained with the steam leaving the boiler.

In other words, bubbles need not" be particularly stable to cause boilerfoaming. The stability of the bubbles need only be such that the bubbleslast but a very few seconds after passing the plane of the water levelindicated in the Water glass.

I have now found that the slight degree of stabilization of bubbleswhich suffices to cause foaming of boiler water may be largely orcompletely inhibited by the addition to the water of a high molecularweight composition formed by a reaction of polymerized fatty acidsderived from drying or semi-drying oils with a nitrogen containingsubstances selected from the group comprising alkylene diamines,polyalkylene polyamine, hydroxy alkyl amines containing hydrogendirectly attached to nitrogen and a primary hydroxy group, and likecompounds.

It is therefore an important object of the present invention to providemethods and compositions for preventing foaming in steam boilers,particularly by incorporation with said Water of the above disclosedcondensation products of polymerized higher fatty acids with aliphaticnitrogen containing compositions.

Other and further features and objects of the 2 present invention willbecome apparent from the following detailed disclosure and appendedclaims.

The polymerized higher fatty acids used as such or in the form of theiresters in the preparation of the foam inhibiting compounds of thepresent invention are derived by methods known in the art from drying orsemi-drying oils, fatty acids liberated by saponification of such oils,or esters of such fatty acids.

The relationship, for instance, of linoleic acid to its polymerizationproducts may be roughly indicated by the following formulae:

R-G-OH I 1 EO-O-R-R-C-OH II I I i no-o-a-a-o-on m A COH wherein Rrepresents an unsaturated hydrocarbon chain.

It will be seen that the dimeric acid (Formula 11) is dibasic, and thatthe trimeric acid (Formula III) is tribasic. It is not believed thatpolymers higher than the trimer are formed.

In general, a polymerized higher fatty acid may be reacted with theabove mentioned basic nitrogen containing compositions either in theform of the free acid or in the form of esters thereof. It is mostconvenient to use directly the acid or the ester obtained as a productof any one of the several available polymerization processes.

If desired, the free fatty acids derived by saponification from a dryingor semi-drying oil such as soy bean oil, corn oil, linseed oil or thelike may be polymerized by a simple heat treatment, for instance, at 265to 275 C. for from 17 to 18 hours. The product is then subjected todistillation at from two or three millimeters of mercury for removal ofthe unpolymerized fraction. Such a process is disclosed in BritishPatent No. 428,864 issued to Imperial Chemical Industries, Ltd.

It is also possible to subject the original drying or semi-drying oilsto a heat treatment at, say,

285 to 295 C. for twenty hours followed by saponification and fractionaldistillation under vacuum of the liberated fatty acids to removetherefrom the glycerine and the unpolymerized fatty acids. This methodof preparation is also disclosed in the above identified British PatentNo. 428,864.

Still another method of preparing polymerized higher fatty acid materialinvolves the methanolysis of soy bean oil or other vegetable oils,removal of liberated 1 glycerine, polymerization of the separated methylesters by heat treatment or, optionally, by catalytic means, and finalseparation of the polymerized methyl esters from the unpolymerizedmethyl esters by distilling oil the latter.

The extent of polymerization effected in any one of the above outlined(procedures :depends, inter alia, on the length of time :during whichpolymerization is carried out. For the purposes of the presentinvention, the dimeric acids and their esters are preferred, and thepo1ymeriza-- tion is regulated accordingly. 7

It is apparent that if a dimeric acid (Formula II) is reacted, forinstance, with ethylene di- This "diacylated product should have a:molecuilar 'weight "of approximately 5.84, being a'formed :from two-m'olecules :of :linoleic acid (molecular 'weight 280) and cone.molecule ethylene ,diamine (molecular weight 60), two molecules ofwater '(molecular'weight 18) being split off. Neverthe- -:less, the:reaction :product of the :di-meric acid derived from linoleicgacidrwith methylene zdiamine may have an actual .average molecularweight varying from 750 up to 2,800 or higher. This is believed due tothe formation of linear condensation products, for instance, "two ormore of the molecules designated by Formula IV being joined together byreaction of the free carboxyl groups at the ends of Formula. IVwithethylene diamine. If

I have found that for the purposes of inhibiting foam formationfin-boiler water, condensation products of the above indicated nature musthave a molecular :weight of .least 1,000, .and that, .-in general, theefficiency of such compounds in- .creases with .molecular weight.

.To illustrate .morefullythe preparation of the foam inhibitingcompounds of :thepresentinvention, I will describe .hereinbelow in somedetail sthe preparation of a polymerized soy bean fatty (acids v"amidebya process including,-as.aninter- ,mediate step, .the preparation .of a.methyl ester of ithesoybeanfatty acids. Such methanolysis can 'beeffected-by the .use -of 0.25 partsodium .hydroxicle, sodium vmethoxideor potassium .hy- .droxide. The reaction .iseffected by using 2.5'0rmore moles of methanol in excess of that re- 'quired, and heating at-'7.0 C.w.for two .hours. [Alkali -.-as sodium hydroxide mustbe=maintained in the :reaction mixture .in order to obtain as 'to settlefor two hours.

.cooled and one kilogram 10f iwater added to the mixture. When themixture hasxcooledto 40 C.,

the agitator is shut off and the mixture allowed After settling, crudeglycerine (4.5 kilograms plus 1.0 kilogram water) is withdrawn from thebottom of the kettle until methyl esters (lighter color) appear in thedrainage. The methyl esters removed from the kettle are covered .in aseparatory funnel and returned to the kettle. Five gallons of water areadded .to the kettle, the mixture is heated to C. with agitation, andallowed to settle for thirty min utes. The water is withdrawn from thebottom of the kettle, and the washing operation repeated twice. Thekettle is plosed and the contents heated to 110 C. under a ;pressure of:fifteen millimeters to remove final traces -of water. :A yield of29'kilograms of methyl-esters is-obtained.

Numerous catalysts, including sulfur dioxide and anthraquinone, may beemployed :for :the

ffected by distilling ;-at pot temperatures up to :2? 0 -C. and by the:uSe of super-heatedsteam yin itheyfinal stagesnf thedistillation.:Reduced pressures of 5 to :10 millimeters ;,ar e zneeessa-ryformemOVaIrOf :alhbut :tracesof :monomeric esters. 'I-,he polymerization.and distillation ,steps, as men.- formed in 1a fifteen-gallon uarnishz-kettle, :are describediin .:detail as follows:

- :tube for introducing ;ga-s t-into :the ,kettle to -,a

gas :from the top.

.for eight hours.

point near the bottom, and a tube for removing In the kettle --,areplaced 34 kilograms of methyl esters, sand. heat and t :-tion areapplied. The esters ,are :warmed to 100 20., the kettle isevacuated-slowly :to ififte'en millie meters pressure :after having been:closed, and

sulfur dioxide run in through the stainless steel The gas .outlet at thetop :of th kettle ,kettle; and-withdrawn continuously during therm-.mainder of the reacticn'period. The sulfur idioxide is absorbed bybubbling through water. The mixture inthe kettle is :heated-to 30 0.zanjd maintained 'at'a temperature or .295" ;to 300 ThemiX-ture is:then :allowed-zto cool to .200" .C., and vacuum ;is slowly applied :todistill unbodied methyl -=est,ers (monomer);

The monomer is distilled under ireduced pressure .until a temperature:Land:pressureror-z'lfl" C.=.and .five to ten millimetersareobtained.Anyn'remaining monomeric -fat esters arezremoved by superheated; steam.Theresiduall dimeric esters inathze "kettle are then :cooled :to roomwtemperature :in

vacuo.

The distillation yields :1937 kilograms .of monomer and 1,319 kilogramsof rresidual-dimertc ses'ters. 1

Polymerization .can also be carried out by simple heating at about SOOC. The effects on soy bean methyl esters of such a bodying treatmentcarried out for from 2 to hours is tabulated as follows:

tylene diamine; dibutylene triamine and the like. Instead of thepolyalkylene polyamines, I may use the hydroxy alkyl amines containinghydrogen directly attached to nitrogen and a primary hydroxy group, suchas monoethanolamine, di-

. Residual Refractive Viscosity in Specific Trimer Dimer/Trimer Bodied Et Index at Centipoises Gravity at Monomer Dimerand .Bati

' S 8 C. at 30 C. 30/15.6 Residue (molar) Hours Per Cent j Per Cent PerCent Per Cent The polyamide can be prepared from residual dimeric fatacids or esters thereof. The preparation runs smoothly both with estersand acids, but the reaction is somewhat faster with the acids. Thepreparation of polyamide from the free dimeric acid is described asfollows:

In a fifteen-gallon experimental varnish kettle, 15.82 kilograms ofresidual dimeric fat acids are heated to 150 C. in an atmosphere ofcarbon dioxide and 2.30 kilograms of aqueous ethylene diamine is addedslowly with vigorous stirring. The reaction proceeds with the loss ofwater from the kettle due to evaporation of water added in the diaminesolution and the dehydration of diamine salts to give amide linkages.After all of the diamine is added (approximately two hours), thetemperature is raised to 150 G. Then over a period of ninety minutes,the pressure on the reaction mixture is reduced slowly to thirteenmillimeters and the temperature is raised to 200 C. If too rapid a riseof temperature or lowering of pressure is permitted, excessive foamingmay result. The reaction mixture is held at 200 C. at thirteenmillimeters pressure for ten minutes, and then run into a vat under anatmosphere of carbon dioxide. The charge is allowed to cool untilhardened. Then it is removed by inverting and tapping the sides of thevat.

Residual dimeric fat esters may be used instead of acids. With esters,the diamine can be added directly to the esters and the mixture heatedto 110 C. Water begins to distill and the reaction temperature needs tobe maintained so that the temperature of the distilling vapors does notexceed to C. A short fractionating column which permits some separationof ethylene diamine from water and alcohol is helpful. When 55% of thecalculated amount of distillate has been collected, the temperature israised to C. and then the pressure reduced slowly to fifteenmillimeters, and at the same time the temperature is raised to 200 C.

The preparation of a polyamide from linseed oil is carried out similarlyto the preparation described hereinabove using soy bean oil as theoriginal starting material. In all such preparations of polyamides, thetime and reaction conditions are regulated so as to effect the formationof products having molecular weights of at least 1,000.

Similar foam inhibiting compounds having molecular weights of at least1,000 may be prepared by reacting polymerized higher fatty acids oresters thereof with polyalkylene polyamines such as diethylene triamine,triethylene tetramine. tetraethylene pentamine, with propylene diamine,dipropylene triamine, tripropylene tetramine, bu-

ethanolamine, triethanolamine, methyl diethanolamine, and, in general,primary, secondary and tertiary hydroxy alkyl amines or. alkanol amines,such as propanol amines, butanol amines, ethanol butanol amines,diethanol butanol amines, alkyl derivatives of hydroxyl alkyl amines oralkanol amines, alkanol alkylene diamines, alkanol polyalkylenepolyamines, ether derivatives of hydroxy amines such as a monoethylether of diethanol amine, amino derivatives of polyhydroxy compoundssuch as l-amino propane diol-2,3, and glycerol monoamine and the like.

Melamine may also be used instead of the polyalkylene polyamines forcondensation with polymerized higher fatty acid compounds, as well asthe condensation products of two moles of an alkylene diamine orpolyalkylene polyamine with one mole of a dibasic acid such as tartaricacid, oxalic acid, sucoinic acid, citric acid, maleic acid and malicacid. These condensation products have terminal primary amino groups.

The foam preventing compounds of the present invention were prepared bycondensing under suitable conditions two moles of a polymeric fatty acidcompound with one mole of any one of several of the above discloseddibasic or polybasic amines or hydroxy amines to form a product in whichthe primary amino groups or hydroxy groups are acylated. Good resultsare also obtained by additionally acylating one or more secondary aminogroups when secondary amino groups are present in the acylated amine.

The foam inhibiting compositions of the present invention may beintroduced into steam boiler water in the form of colloidal dispersionsthat may be stabilized with tannin, gum arabic or pectin. If desired,the foam inhibiting compositions may be introduced into the boiler inthe form of a solution in an appropriate solvent, such as iso propylalcohol. The dosages required are generally quite small, on the order ofsome few parts per million of boiler water. In general, from a trace toabout fifty parts per million of foam inhibiting compounds may be addedto boiler water, preferably in combination with tannin. Addition of foaminhibiting compounds may be repeated as required to prevent foaming.

Various details may be varied through a wide range without departingfrom the principles of this invention, and it is, therefore, not mypurpose to limit the patent granted hereon otherwise than necessitatedby the scope of the appended claims.

I claim as my invention:

1. The method of generating steam from a ammraa 2. The method ofgenerating steam :from a boiler water having a tendency tot-foam onboiling,

which comprises dispersing into'said Water in an amount sufiicientsubstantially to inhibit the tendency of said wa'terto foam onjboiling acompound having a molecular weight of "at 'least 'one thousand andcomprising the linear condensation product of 'one molecular proportionof ethylene 8 diamine aniitwo molecular r mportionszofmisdimer ofan-unsaturated'higherifattysacidzderivedhum soy -bean ;oi1xf-attyracids, and :boilingi-the mesultirm dispersion Itogeneratersteamatherefrom.

LEWIS 0.; .GUNDERSQN.

REFERENCES .CITED The following 'aneferences are of erecord in the =fi1e.of this patent:

UNITED STATES PATENTS Number Name Date 1,892,857 Spellmeyer "Jan. 3,21933 2,341,632 Robinson e'txal. :Apr. 4,31%4 2,347,178 Fritz et a1...2\pr."25,;19%4 2,379,413 Bradley wJuly 3,?1945 FOREIGN N umber -Country.Da'te 547,189 iGreattBritain Aug. 18,

1. THE METHOD OF GENERATING STEAM FROM A BOILER WATER HAVING A TENDENCYTO FOAM ON BOILING, WHICH COMPRISES DISPERSING INTO SAID WATER IN ANAMOUNT SUFFICIENT SUBSTANTIALLY TO INHIBIT THE TENDENCY OF SAID WATER TOFOAM ON BOILING A COMPOUND HAVING A MOLECULAR WEIGHT OF AT LEAST ONETHOUSAND AND COMPRISING A LINEAR CONDENSATION PRODUCT OF ONE MOLECULARPROPORTION OF ETHYLENE DIAMINE AND TWO MOLECULAR PROPORATIONS OF A DIMEROF AN UNSATURATED HIGHER FATTY ACID DERIVED FROM A MEMBER OF THE GROUPCONSISTING OF LINSEED OIL FATTY ACID AND SOY BEAN OIL FATTY ACIDS, ANDBOILING THE RESULTING DISPERSION TO GENERATE STREAM THEREFROM.